1. Field of the Invention
The present invention relates to a scroll type compressor that changes the volumetric capacity of a compression space formed with a fixed scroll member and an orbiting scroll member to compress the on-board coolant.
2. Description of the Related Art
In scroll type compressors of the prior art, in which a compression space is formed by fitting together a fixed scroll member that is provided with a fixed scroll in the form of a coil and an orbiting scroll member that is provided with an orbiting scroll in the form of a coil wherein the aforementioned orbiting scroll member makes an orbiting movement relative to the fixed scroll member, the volumetric capacity of the aforementioned compression space expands and contracts repeatedly to perform intake, compression and discharge. Thus, the lubrication and sealing of the sliding contact surface between the fixed scroll member and the sliding scroll member are crucial factors.
Accordingly, the scroll type compressor disclosed in Japanese Patent Unexamined Publication No. H3-149391 includes a rotary displacement type oil pump in its structure, so that a sufficient quantity of lubricating oil can be reliably supplied to the bearings regardless of the flow rate of the lubricating oil supplied to the compression work space. With this, a large quantity of lubricating oil can be assured even when high loads are applied to the revolving drive bearing, the eccentric bearing and the first main bearing.
Also, the scroll type compressor disclosed in Japanese Patent Unexamined Publication No. H3-61689 is provided with a cylinder section towards the direction of reciprocal movement of the Oldham's coupling on the wall surface facing opposite the external circumferential surface of the Oldham's coupling which prevents auto rotation of the orbiting scroll member. A liner is provided that moves back and forth within the aforementioned cylinder section in conformance with the operation of the Oldham's coupling to push out the lubricating oil. This structure allows the quantity of supplied oil to be increased as the number of rotations in the drive unit increases.
Likewise, the Japanese Patent Unexamined Publication No. H3-105093 discloses a structure in which a pressurized passage, which is subject to a centrifugal force from the drive shaft, is formed in the drive shaft towards the outside in the direction of the radius of the drive shaft, constituting a so-called centrifugal pump to supply lubricating oil.
However, with the scroll type compressors in the examples quoted above, it is required that a non ferrite material such as aluminum be used for the fixed scroll member and the orbiting scroll member to reduce weight and cost, and a problem arises therefrom. Because of the high back pressure on the orbiting scroll member, it is pressed towards the fixed scroll member, and as a result, the sliding area where the orbiting scroll member and the fixed scroll member are in contact with each other tends to seize, even though the quantity of oil supplied to the sliding contact surface is increased. Thus, it is necessary to reduce the back pressure applied to the orbiting scroll member.
Also, since the drive shaft is provided over the high-pressure side, where a drive means is provided, through the low-pressure or intermediate drive side where the orbiting scroll member is provided, a force is constantly applied towards the orbiting scroll member side by the pressure differential between the high-pressure and low-pressure regions or the pressure differential between the high-pressure and intermediate pressure regions. Because of this, it is required that a bearing (thrust bearing) be provided at the end of the drive shaft to receive the load applied by this force.
However, when the load is large, the thrust bearing itself can seize, and as the load is applied constantly, the service life of the thrust bearing is shortened.